The invention concerns spinal osteosynthesis systems, in particular for anterior fixation.
A spinal osteosynthesis system for anterior fixation is known from the document WO 94/06360. Said system includes a longitudinal plate and one arm made in one piece with the plate, extending from one end of the latter and inclined relative to its longitudinal direction. This arm receives two bone screws to be anchored in a vertebra. The other end of the plate has two oblong orifices parallel with each other and intended to receive two respective bone screws to be anchored in another vertebra. The two fixation vertebrae are separated by the vertebra intended for arthrodesis. The oblong orifices make it possible to adjust the longitudinal position of the two screws relative to the arm. As the number of components to be assembled is limited, this system can be fitted quickly during an intervention. However, the main component of this system is bulky, which makes it difficult to introduce into the body by the endoscopic route. Moreover, this main component is not designed to be adapted to the configuration of the patient""s vertebrae with a view to optimizing its position or the quality of its fixation to the vertebrae.
An object of the invention is to provide a system which at one and the same time is quicker to fit and is easy to introduce by the endoscopic route.
To achieve this object, the invention provides a spinal osteosynthesis system for anterior fixation, comprising first and second arms which can each receive bone screws, and a longitudinal plate which can rigidly link the arms, the plate being made in one piece with the first arm, and the system comprising means for adjusting a longitudinal position of the second arm on the plate.
Thus, with the second arm being separable from the plate, the system is made up of elements which are small in size and can be introduced into the body by the endoscopic route as well as by the normal route. Disregarding the screws, the essential elements of the system are two in number, so that installation of the system (assembly and relative positioning of the components) in the body is a simple matter. The operating time thus remains short. The presence of the plate made in one piece with the first arm makes it possible to envisage reducing very substantial kyphosis by the anterior route by means of leverage on the vertebra associated with this arm. Moreover, the plate can be placed in the most posterior position possible on the vertebral body, allowing free access to the damaged vertebra or to the graft. Finally, with a view to adapting it to the configuration of the vertebrae, the second arm can be easily shaped since it is independent of the rest oft he system.
The invention may advantageously present one or more of the following characteristics:
the plate has at least one orifice for adjusting the longitudinal position;
the orifice is of oblong shape;
the orifice has, at least one end, a continuation with a width smaller than the width of a central part of the orifice;
the system includes an adjusting or fixation screw which can be fixed to the second arm and can slide in the orifice;
the system comprises at least one fixation screw which can be engaged in one of the bone screws associated with one of the arms, in order to fix the arm to the bone screw;
the arm has an orifice which can be interposed between the bone screw and the fixation screw;
the fixation screw is the adjusting screw;
the second arm and the plate have centering faces which can come into mutual contact in order to center the arm relative to the plate;
the arm and the plate each have two centering faces which can form a male-female assembly;
the centering faces are plane;
each arm can be bent manually.